Shortcut to cycle through open tabs

Summary by @shoogle:

Use Ctrl+Tab and Ctrl+Shift+Tab to switch to the next or previous part tab, including the main score.

• That's Ctrl on all platforms; not Cmd on macOS. (In Qt, it's called the Meta key on macOS.)
• It should only happen when the notation view or the part tab bar has focus.

Outside the score, those shortcuts should continue to do what they do now.

Optional extra: If another tabbed area has focus, the shortcuts could cycle those tabs. E.g.:

• If you're in the Palettes, Layout, or Properties panels, these shortcuts could cycle those panels.
• If you're in Preferences, the shortcuts could cycle the vertical tabs (General, Appearance, Canvas, etc).

In general, the shortcuts would look at parent/ancestor UI objects and cycle the first set of tabs it finds.

Original content:

Your idea

Alt+Tab (Win) and Command+Tab cycles through apps in the OS. Shortcuts with the ~ key instead of Tab cycle between windows in the same app. Since MSS doesn't support multiple windows in an app instance, a shortcut to Alt+~ or Command+~ to cycle through open tabs (like different parts), would help navigating scores with a large number of parts. This may also be implemented as a previous tab/next tab shortcut pair in Preferences>Shortcuts..

Problem to be solved

Currently in MSS v4.3.2, F6 cycles through some tabs (Palettes, Instruments, the Score, etc.) When the Score is highlighted, the left/right arrow keys next select the X button and then the next open tab, etc. This is cumbersome and unintuitive. In scores with many parts, mousing to the tab can be much slower than a prev/next keyboard shortcut.

Prior art

No response

Additional context

No response

Checklist

• This request follows the guidelines for reporting issues
• I have verified that this feature request has not been logged before, by searching the issue tracker for similar requests

Start by tracing keyboard handling from the notation view and part tab bar, confirming how focus is detected and how the main score and part tabs are ordered. Implement Ctrl+Tab and Ctrl+Shift+Tab only while those areas have focus, preserving current behavior elsewhere, then verify cycling in both directions; consider the optional panel and Preferences tab behavior separately.